Minutes of the Tracker Meeting

March 25, 2004



1.     Nicola: T/V results from the meeting in Bari

2.     Jeff: new drawings and parts spread sheet

3.     Martin: status of bottom tray assembly drawings needed in Pisa

4.     Martin or Mike: status of bottom tray closeout drawings and machining (critical now!); Jeff: PO status

5.     Riccardo & Ben: status of prepreg procurement from COI (specifications issues)

6.     Jerry or Dave: bias circuit status and plans

7.     Riccardo: tray production status; ESPI document; shipping plans (e.g. Plyform to Pisa and back)

8.     Nicola: readiness for mid tray vibration testing. Release of documentation.

9.     Dave: MCM status

10.  Robert: schedule and critical path to be presented to DOE/NASA next week (see attachments)

11.  A.O.B.


Action Items:

1.     Robert: give Jeff Tice information to procure cables for T/V testing

2.     Riccardo: check whether glass beads could be used to ensure bondline thicknesses in the bottom tray assembly.

3.     Mike: correct the epoxy called out in the BOM for closeout assembly (and other tray drawings)

4.     Riccardo: help Plyform correct the prepreg RFQ with the right specification table

5.     Jeff Tice: procure Keenserts for the grid simulators

6.     Riccardo: send the ESPI procedure to Robert for release.

7.     Robert: release the tray vibration procedure.


Old Action Items:

8.     Martin: send out the bottom tray assembly drawing check prints

9.     Riccardo: check Plyform drawings against the latest releases for mid-tray production

10.  Martin: send Sandro known constraints on the MCM mounting pin head

11.  John Ku and Mike Opie: draft or redlined static and vibe test plans

12.  Jim: find a designer to revise the static test and vibe test tooling for the new interface


Nicola reported that the thermal-vacuum meeting in Bari was successful. The results presented can be found on the Bari web page, http://www.ba.infn.it/~glast/. The distribution of temperature in the tower is reasonable, but we must wait for the correlation analysis to be completed to know the details.

Tom M. added that all 3 goals were achieved:

  1. thermistor vs thermocouple correlation
  2. evidence that the design is reasonable, with gradients less than predicted (parasitics still need to be accounted for in the analysis)
  3. 7 cases of thermal-balance data to correlate with models


Nicola reminded us of some anomalies seen in the test

1.     power instabilities, especially at the end of the test. Current vs voltage was measured in air and vacuum. Near the end of the test some nonlinearities were seen.

2.     offset of thermistor readings, which had to be corrected to evaluate the temperature

Nicola said that a written report will be out in the next couple of weeks. We can expect a correlation report in 4 weeks.


We discussed the next T/V test:


Robert asked about the bottom-tray assembly drawings. Mike reported that he has been reviewing them with Martin. He was concerned that the glue joints could become too small. He investigated and found that an epoxy bond line should be no less than 5 mils (125 microns) thick. Mike and Martin recommend mixing 5-mil glass beads into the glue. This is done by COI for the bottom-tray closeout lamination, for example. Riccardo thought that the fixturing technique should ensure adequate bond line thickness, and he said that they can be checked in a dry fit-up check. Others thought it would be best to avoid this extra work by employing beads. Riccardo will check with Sandro and Plyform whether 5-mil glass beads could be used to ensure bondline thickness.


Mike also has reviewed the closeout drawings. He found issues with the glue callouts for insert bonding. Riccardo verified that it should be Hysol EA934NA. Also, Mike was critical of the fact there there is not a separate drawing of the carbon-carbon piece. The dimensions are just called out in the BOM. Robert emphasized the urgent need to get the machining drawings to COI. The assembly drawing is for Plyform. Also, COI has already completed the lamination of the M55J and CC. Jeff said that the PO is ready to go, pending the drawings.


Ben talked about the recent issues with the prepreg procurements. He confirmed that Tg=170C is the minimum glass transition temperature. It appears that the wrong set of properties accidentally got sent to COI. Riccardo has the correct values and will forward them to Plyform to correct the RFQ.


Riccardo reported on Plyform progress. They are still doing sandwiches and are preparing closeouts, including painting. All of the inserts are in. By end of next week the bare panels should be assembled. ESPI testing will be done the following week, at a rate of about 4 to 5 panels per day. The ESPI procedure will be sent to Robert for release in day or two. Plyform has made a shipping crate and will ship the panels to Pisa by courrier. Riccardo estimated 2 days maximum each way. Pisa will try to get the first few panels early to start on the ESPI. Bonding of tungsten and bias circuits will begin after the trays return to Plyform, which will be April 12 at earliest.


Jerry reported on the bias circuit status. 42 are on the way to Pisa. 2 more are being measured today by the optical comparator (results were good). Artwork was received from Parlex this morning to approve tie bars. Once that is settled, then they are off and running. We expect to get the first 50 April 13. Jerry talked to the Parlex VP about them doing better with schedule performance.


Arthur reported on his work on drawings for the interface hardware. Martin has redlined them twice, so they are nearly ready to go. He and Mike will provide them to Natalie for distribution, including to Pisa. Jeff will go to Advanced Machining to look into procuring 36 fastener sets (3 towers worth).


Mike said we also need to prepare soon the shim drawings.

Keenserts also need to be procured. They are stock items; Jeff will do the order.

The plan is to order the bushings together with grid simulator, because the manufacturer needs to match the two to get them pressed in.


Nicola reported that the vibration procedure document for trays is on the Bari web site for release. Robert will get it released. They will be ready to start testing trays April 20 (the expected schedule date).


Tom V. brought up the issue of whether the tray test is required and necessary. We decided that it should be done for the first sets of trays, at least, and we can reconsider the issue later, especially if there is a schedule crunch.


Dave reported on the MCM status. Flight production started as of Tuesday. Teledyne will start ramping up to the full rate of 25 per week. April 16 is expected to be the first delivery, although Dave needs to confirm this with Teledyne. A week later we can expect another 25.